An electrophotographic image forming apparatus includes a photosensitive drum, a developing roller, and a toner supply roller. Toner accommodated in a toner container is conveyed to the developing roller by the toner supply roller, and an electrostatic latent image formed on the photosensitive drum is developed with the toner supplied by the developing roller. All the toner supplied to the developing roller is not used for the development of the latent image but a part of the toner remains unused in the developing roller. A long-term use of the apparatus results in accumulation of the unused toner on the developing roller.
Hence, it has been proposed to perform toner cleaning operations for the developing roller to remove the toner accumulated thereon. The cleaning operations are performed whenever the apparatus is powered and/or after making a predetermined number of copies. It has also been proposed that the toner cleaning operation for negatively charged toner be performed by applying a bias voltage ranging from +100 to +500 V to the supply roller. With such a toner cleaning operation, the toner supply roller can remove the toner accumulated on the developing roller.